Anode active material, method for preparing same, anode composition, anode for lithium secondary battery comprising same, and lithium secondary battery comprising anode

Abstract

An anode active material according to the present application comprises a silicon-based active material having a grain size of about 300 nm or less. The silicon-based active material has a value of about 2.00 or less as defined by the formula of (D90-D10) / D50, and the silicon-based active material includes one or more selected from SiOx (x=0) and SiOx (0<x<2) and includes about 70 parts or more by weight of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material. In the formula, D90, D10, and D50 mean particle diameters corresponding to 90%, 10%, and 50%, respectively, based on volume in the size distribution.

Description

Negative electrode active material, method for producing negative electrode active material, negative electrode composition, negative electrode for lithium secondary battery including the same, and lithium secondary battery including the negative electrode

[0001] The present application relates to a negative electrode active material, a method for producing a negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

[0002] Due to the rapid increase in fossil fuel use, the demand for alternative or clean energy is increasing, and as part of this, the field of most active research is power generation and storage using electrochemical reactions.

[0003] A representative example of an electrochemical device that utilizes this electrochemical energy is the secondary battery, and its applications are expanding. For example, with the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used. Furthermore, active research is being conducted on methods for manufacturing high-density electrodes with even higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries.

[0004] Unlike spherical silicon particles formed by melting existing silicon raw materials and gas atomizing them, it was found that when the cooling rate is increased through a low-temperature sonicated substrate, grain growth can be reduced, and the resulting silicon-based active material can have a small grain size and a uniform particle size distribution.

[0005] Accordingly, the present application provides a negative electrode active material having a relatively small crystal grain size and a uniform particle size distribution, a method for producing the negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

[0006] One embodiment of the present specification includes a silicon-based active material having a crystal grain size of about 300 nm or less, wherein the silicon-based active material has a value defined by the following formula 1 of about 2.00 or less, and the silicon-based active material comprises SiOx (x=0) and SiOx (0 <x<2)로부터 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 약 70 중량부 이상 포함하는 것인 음극 활물질을 제공한다.

[0007] [Formula 1]

[0008] (D90 - D10) / D50

[0009] In the above equation 1,

[0010] D90, D10 and D50 represent the diameters of particles corresponding to 90%, 10% and 50% by volume in the size distribution, respectively.

[0011] In another embodiment, a method for producing an anode active material is provided, comprising: a step of melting a silicon raw material; and a step of cooling the melted silicon raw material to form a silicon-based active material; wherein the step of cooling the melted silicon raw material to form the silicon-based active material includes a step of cooling the melted silicon raw material by spraying it onto an ultra-vibration low-temperature substrate, wherein the silicon-based active material has a crystal grain size of about 300 nm or less, and wherein the silicon-based active material has a value defined by the following formula 1 of about 2.00 or less.

[0012] [Formula 1]

[0013] (D90 - D10) / D50

[0014] In the above equation 1,

[0015] D90, D10 and D50 represent the diameters of particles corresponding to 90%, 10% and 50% by volume in the size distribution, respectively.

[0016] In another embodiment, an object of the present invention is to provide a negative electrode composition comprising a negative electrode active material according to the present application; a negative electrode conductive material; and a negative electrode binder.

[0017] In another embodiment, there is provided an anode for a lithium secondary battery, comprising: a negative electrode current collector layer; and a negative electrode active material layer provided on one or both sides of the negative electrode current collector layer, wherein the negative electrode active material layer comprises a negative electrode composition according to the present application or a cured product thereof.

[0018] Finally, a lithium secondary battery is provided, including: a cathode; an anode for a lithium secondary battery according to the present application; a separator provided between the cathode and the anode; and an electrolyte.

[0019] The negative active material of the present invention is a silicon-based active material, including SiOx (x=0) and SiOx (0 <x<2)로부터 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 약 70 중량부 이상 포함하는, 즉 Pure Si 활물질을 가지면서 이에 따른 문제점인 충방전에 따른 부피 팽창의 문제를 해결한다.

[0020] In the case of a negative active material according to one embodiment of the present invention, unlike spherical silicon particles formed by melting a conventional silicon raw material and gas atomizing it, when a cooling rate is increased through a sonicated substrate to which low-temperature ultrasonic waves are applied, the silicon-based active material produced by reducing the growth of crystal grains has a small crystal grain size and a uniform particle size distribution.

[0021] For example, by forming a standing wave within the surface that is atomized through the power of ultrasonication, it is possible to form droplets with a particle size in the range of equation 1, and by using a low-temperature substrate instead of conventional air, the cooling rate increases and thus grain growth is reduced, thereby satisfying a specific range of grain sizes.

[0022] Accordingly, the formation of cracks in the active material due to lithium insertion / de-insertion can be suppressed by reducing the crystal grain size, and also, by improving the grain size within the range of Equation 1, the problem of reduced life performance due to uneven charge / discharge within the electrode can be solved as lithium ions are uniformly introduced into the lithium electrode.

[0023] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0024] Figure 1 shows an enlarged view of a silicon-based active material according to one embodiment of the present application.

[0025] Figure 2 is a flowchart exemplarily showing a method for manufacturing a negative electrode active material according to one embodiment of the present application.

[0026] Figure 3 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to one embodiment of the present application.

[0027] Figure 4 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present application.

[0028] Figure 5 is a diagram showing a manufacturing process of a silicon active material according to Example 1 of the present application.

[0029] Figure 6 is a diagram showing a manufacturing process of a silicon active material according to Comparative Example 1 of the present application.

[0030] Figure 7 is a diagram showing a method for calculating the crystal grain size according to one embodiment of the present application.

[0031] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will appreciate that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to facilitate understanding of various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated relative to other elements. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may often not be depicted so as not to obscure the spirit of various embodiments of the present invention.

[0032] Before explaining the present invention, some terms are first defined.

[0033] When a part of this specification is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0034] In this specification, ‘p to q’ means a range of ‘p or more and q or less.’

[0035] In this specification, "specific surface area" is measured by the BET (Brunauer, Emmett, Teller) method, and is calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using, for example, BELSORP-mino II of BEL Japan. In this application, the BET specific surface area may mean the specific surface area measured by the above measurement method.

[0036] In this specification, "Dn" means particle size distribution, and means the particle size at the n% point of the cumulative distribution of particle numbers according to particle size. For example, D50 is the particle size (average particle size) at the 50% point of the cumulative distribution of particle numbers according to particle size, D90 is the particle size at the 90% point of the cumulative distribution of particle numbers according to particle size, and D10 is the particle size at the 10% point of the cumulative distribution of particle numbers according to particle size. Meanwhile, the average particle size can be measured using a laser diffraction method. For example, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the difference in diffraction pattern according to particle size is measured when the particles pass through a laser beam, thereby calculating the particle size distribution.

[0037] In one embodiment of the present application, particle size or particle diameter may mean the average diameter or representative diameter of each grain forming the metal powder.

[0038] As used herein, the term "a polymer comprises a monomer as a monomer unit" means that the monomer participates in a polymerization reaction and is included as a repeating unit within the polymer. As used herein, "a polymer comprises a monomer" is interpreted to mean that the polymer comprises the monomer as a monomer unit.

[0039] In this specification, the term 'polymer' is understood to be used in a broad sense including copolymers unless 'homopolymer' is specified.

[0040] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-converted molecular weights measured by gel permeation chromatography (GPC) using monodisperse polystyrene polymers (standard samples) of various degrees of polymerization commercially available for molecular weight measurement as standard materials. In this specification, molecular weight means weight average molecular weight unless otherwise specified.

[0041] Typically, a secondary battery, or lithium secondary battery, is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. For example, in the case of a lithium secondary battery, the negative electrode includes a negative electrode active material that inserts and deintercalates lithium ions from the positive electrode. Silicon particles with a high discharge capacity can be used as the negative electrode active material.

[0042] Recently, as the demand for high-density energy batteries increases, research is actively being conducted on methods to increase the capacity by using silicon compounds such as Si / C or SiOx, which have a capacity about 10 times greater than that of graphite materials, as a negative electrode active material. However, in the case of silicon compounds, which are high-capacity materials, compared to the graphite used in the past, although the capacity is large, there is a problem that the volume rapidly expands during the charging and / or discharging process, which cuts off the conductive path and deteriorates the battery characteristics.

[0043] Accordingly, in order to solve such problems when using silicon-based compounds as negative electrode active materials, various methods are being studied, such as a method for controlling the driving potential, a method for additionally coating a thin film on the active material layer, a method for controlling the particle size of silicon-based compounds, a method for suppressing the volume expansion itself, or a method for preventing the conductive path from being cut off. However, since the above methods may actually lower the performance of the battery, there are limitations in their application, and there are still limitations in the commercialization of negative electrode batteries with a high content of silicon-based compounds.

[0044] The present invention provides a silicon-based active material, a method for producing the negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode, which can prevent damage to a conductive path due to volume expansion of the silicon-based compound even when the silicon-based active material is used as a negative electrode material to improve capacity performance.

[0045] Hereinafter, the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily practice it. However, the present invention can be implemented in various different forms and is not limited to the following description.

[0046] One embodiment of the present specification includes a silicon-based active material having a crystal grain size of about 300 nm or less, wherein the silicon-based active material has a value defined by the following formula 1 of about 2.00 or less, and the silicon-based active material comprises SiOx (x=0) and SiOx (0 <x<2)로부터 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 약 70 중량부 이상 포함하는 것인 음극 활물질을 제공한다.

[0047] [Formula 1]

[0048] (D90 - D10) / D50

[0049] In the above equation 1,

[0050] D90, D10 and D50 represent the diameters of particles corresponding to 90%, 10% and 50% by volume in the size distribution, respectively.

[0051] In one embodiment of the present application, the silicon-based active material may have a value defined by Equation 1 of about 2.00 or less, for example, about 1.98 or less, or about 1.97 or less, and may be 1.20 or more, 1.50 or more, or 1.60 or more.

[0052] The silicon-based active material according to the present application forms a standing wave within the surface that is atomized by the power of ultrasonication, and thus can have a value of Equation 1 within the above range. Accordingly, as lithium ions are uniformly introduced into the lithium electrode, the problem of reduced life performance due to uneven charging and discharging within the electrode can be solved.

[0053] The negative active material of the present invention is a silicon-based active material, including SiOx (x=0) and SiOx (0 <x<2)로부터 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 약 70 중량부 이상 포함하는, 예를 들면, Pure Si 활물질을 가지면서 이에 따른 문제점인 충방전에 따른 부피 팽창의 문제를 입도 조절(식 1) 및 결정립의 크기를 일정 범위로 조절하여 해결한다.

[0054] Figure 1 is an enlarged view of a silicon-based active material according to one embodiment of the present application. The silicon-based active material (1) is composed of a plurality of crystal structures (2), and according to one embodiment, it can be confirmed that the crystal structures have a crystal grain distribution of about 1 nm to 300 nm. In addition, the space between crystal structures can be defined as a grain boundary. In addition, the crystal structure can generally be expressed as a crystal grain.

[0055] In one embodiment of the present application, the silicon-based active material is SiOx (x=0) and SiOx (0 <x<2)로부터 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 약 70 중량부 이상 포함할 수 있다.

[0056] In one embodiment of the present application, the silicon-based active material includes SiOx (x=0), and may include about 70 parts by weight or more of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material.

[0057] In another embodiment, the silicon-based active material may contain about 70 parts by weight or more, for example, 80 parts by weight or more, or 90 parts by weight or more, of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material, and may contain 100 parts by weight or less, for example, 99 parts by weight or less, or 95 parts by weight or less.

[0058] In one embodiment of the present application, pure silicon (Si) particles may be used as a silicon-based active material. Using pure silicon (Si) particles as a silicon-based active material may mean that, based on 100 parts by weight of the total silicon-based active material, pure Si particles (SiOx (x=0)) that are not combined with other particles or elements are included within the above range.

[0059] In one embodiment of the present application, the silicon-based active material may be formed of silicon-based particles having 100 parts by weight of SiOx (x=0) based on 100 parts by weight of the silicon-based active material.

[0060] According to one embodiment, the crystal grain size of the SiOx (x=0) may be about 300 nm or less.

[0061] In one embodiment of the present application, the silicon-based active material may include a metal impurity, and at this time, the impurity may be a metal that may be generally included in the silicon-based active material, and may include, for example, about 0.1 part by weight or less based on 100 parts by weight of the silicon-based active material.

[0062] In the case of silicon-based active materials, compared to the existing graphite-based active materials, the capacity is significantly higher, so attempts to apply it are increasing. However, because the volume expansion rate is high during the charge / discharge process, it is limited to cases where a small amount is mixed with the graphite-based active material and used.

[0063] Therefore, in the case of the present invention, in order to improve capacity performance, only a silicon-based active material is used as an anode active material, and in order to solve the problem of volume expansion due to charge and discharge as described above, the existing problem was solved by controlling the average particle diameter (D50) and crystal grain size of the silicon-based active material itself rather than controlling the composition of the conductive agent and binder.

[0064] In one embodiment of the present application, the crystal grain size of the silicon-based active material may be about 300 nm or less.

[0065] In another embodiment, the crystal grain size of the silicon-based active material may be 300 nm or less, for example, 290 nm or less, 260 nm or less, 258 nm or less, 255 nm or less, or 253 nm or less. In one embodiment, the crystal grain size of the silicon-based active material may have a range of about 10 nm or more, for example, 100 nm or more.

[0066] The above silicon-based active material has the above crystal grain size, and the crystal grain size of the silicon-based active material can be controlled by changing the process conditions in the manufacturing process described below. At this time, by satisfying the above range and ensuring that the grain boundaries are widely distributed, when lithium ions are inserted, the lithium ions are uniformly inserted, thereby reducing the stress applied when lithium ions are inserted into the silicon particles, and thus alleviating the phenomenon of particle breakage. As a result, the life stability of the negative electrode can be improved.

[0067] In one embodiment of the present application, the silicon-based active material includes a crystal structure having a crystal grain distribution of about 1 nm or more and 300 nm or less, and an anode active material is provided in which the area ratio of the crystal structure is about 5% or less based on the total area of ​​the silicon-based active material.

[0068] In another embodiment, the area ratio of the crystal structure based on the total area of ​​the silicon-based active material may be about 5% or less, or about 3% or less, and may be about 0.1% or more.

[0069] The silicon-based active material according to the present application has a crystal grain size of approximately 300 nm or less, so that a single crystal structure can be formed with a relatively small size and satisfy the above-mentioned area ratio. Accordingly, the distribution of grain boundaries can be relatively widened, and thus the aforementioned effects, such as suppression of volume expansion during charge and discharge, can be exhibited.

[0070] In one embodiment of the present application, a negative electrode active material is provided in which the number of crystal structures included in the silicon-based active material is about 20 or more.

[0071] The number of crystal structures included in the silicon-based active material may refer to the number of each crystal structure in Fig. 1. That is, the silicon-based active material itself may be composed of a plurality of crystal structures, and in this case, the number of crystal structures may be about 20 or more.

[0072] In another embodiment, the number of crystal structures included in the silicon-based active material may be 20 or more, 30 or more, or 35 or more, and may satisfy a range of 60 or less, or 50 or less.

[0073] As described above, when the silicon-based active material has a crystal grain size that satisfies the above range and the number of crystal structures that satisfies the above range, the strength of the silicon-based active material itself has an appropriate range, so that when included in an electrode, flexibility can be provided and volume expansion can be efficiently suppressed.

[0074] In the present application, a crystal grain means a crystal particle that is a collection of irregularly shaped microscopic particles in a metal or material, and the crystal grain size may refer to the diameter of an observed crystal grain. That is, in the present application, the crystal grain size refers to the size of a domain that shares the same crystal direction within a particle, and is a different concept from the particle size or particle diameter that expresses the size of a material.

[0075] In one embodiment of the present application, the crystal grain size can be calculated as the FWHM (Full Width at Half Maximum) value through XRD analysis. For example, a method for calculating the crystal grain size can be seen in Fig. 6. In Fig. 6, the remaining values ​​excluding L are measured through XRD analysis of a silicon-based active material, and the crystal grain size can be measured through the Debey-Scherrer equation, which shows that the FWHM and the crystal grain size are inversely proportional. In this case, the Debey-Scherrer equation is as shown in Equation 1-1 below.

[0076] [Formula 1-1]

[0077] FWHM=(Kλ) / (LCOSθ)

[0078] In the above formula 1-1,

[0079] L represents the grain size, K is a constant, θ is the bragg angle, and λ is the wavelength of the X-ray.

[0080] In addition, the shape of the crystal grains is diverse and can be measured three-dimensionally, and the size of the crystal grains can generally be measured using the commonly used circle method and diameter measurement method, but is not limited thereto.

[0081] The above diameter measurement method can be measured by drawing 5-10 equilibrium lines, each of which is L mm long, on a microscopic photograph of the target particle, counting the number of grains z on the lines, and averaging them. At this time, only those that are completely included are counted, and those that cross are excluded. If the number of lines is P and the magnification is V, the average grain diameter can be calculated using the following equations 1-2.

[0082] [Formula 1-2]

[0083] Dm = (L*P*10 3 ) / (zV) (um)

[0084] In addition, the above circle method is a method of calculating the average area of ​​crystal grains by drawing a circle of a set diameter on a microscopic photograph of the target particle and calculating the number of crystal grains within the circle and the number of crystal grains that fall on the boundary line using the following equation 1-3.

[0085] [Formula 1-3]

[0086] Fm = (Fk * 10 6 ) / ((0.67n + z)* V 2 ) (um 2 )

[0087] In the above equation 1-3, Fm represents the average particle area, Fk represents the measured area on the photograph, z represents the number of particles inside the circle, n represents the number of particles in the circular arc, and V represents the magnification of the microscope.

[0088] In one embodiment of the present application, the silicon-based active material may include silicon-based particles having a particle size distribution of about 0.01 μm or more and 30 μm or less.

[0089] The above-mentioned silicon-based active material includes silicon-based particles having a particle size distribution of about 0.01 μm or more and 30 μm or less, which means that it includes a plurality of individual silicon-based particles having particle sizes within the above range, and the number of silicon-based particles included is not limited.

[0090] The particle size of the above silicon-based particles can be expressed by their diameter if they are spherical, but even if they are of a shape other than spherical, the particle size can be measured by comparing them to the spherical case, and the particle size of individual silicon-based particles can be measured by a method generally used in the art.

[0091] Meanwhile, the average particle diameter (D50 particle size) of the silicon-based active material of the present invention is about 1 μm or more and 9 μm or less, for example, about 2 μm to 8 μm, or about 3 μm to 8 μm. When the average particle diameter is within the above range, the specific surface area of ​​the particles is within an appropriate range, so that the viscosity of the negative electrode slurry is formed within an appropriate range. Accordingly, the particles constituting the negative electrode slurry are smoothly dispersed. In addition, when the size of the silicon-based active material is greater than the range of the lower limit, the contact area between the silicon particles and the conductive material is excellent due to the composite composed of the conductive material and the binder in the negative electrode slurry, so that the possibility of the conductive network continuing increases, thereby increasing the capacity retention rate. Meanwhile, when the average particle diameter satisfies the above range, excessively large silicon particles are excluded, so that the surface of the negative electrode is formed smoothly, and thus the phenomenon of uneven current density during charge and discharge can be prevented.

[0092] In the present application, a negative electrode active material is provided, wherein the crystal grain size of the silicon-based active material is about 1 nm or more and 300 nm or less, and the average particle diameter (D50) of the silicon-based active material is about 3 μm or more and 8 μm or less.

[0093] In one embodiment of the present application, the silicon-based active material generally has a characteristic BET surface area. The BET surface area of ​​the silicon-based active material is about 0.01 m 2 / g to 150 m 2 / g, or 0.1 m 2 / g to 100 m 2 / g, or about 0.2 m 2 / g to 80 m2 / g, or 0.2 m 2 / g to 18 m 2 / g. BET surface area is measured according to DIN 66131 (using nitrogen).

[0094] In one embodiment of the present application, the silicon-based active material may exist in a crystalline or amorphous form, for example, and may not be porous. The silicon particles may be spherical or fragment-shaped, depending on the embodiment. Alternatively, the silicon particles may also have a fibrous structure or be present in the form of a silicon-containing film or coating.

[0095] In one embodiment of the present application, the silicon-based active material may have a non-spherical shape and its sphericity is, for example, about 0.9 or less, for example, about 0.7 to 0.9, for example, about 0.8 to 0.9, for example, about 0.85 to 0.9.

[0096] In the present application, the circularity is determined by the following equation 1-A, where A is an area and P is a boundary line.

[0097] [Formula 1-A]

[0098] 4πA / P 2

[0099] In one embodiment of the present application, a negative electrode composition is provided, including the negative electrode active material; a negative electrode conductive material; and a negative electrode binder.

[0100] In one embodiment of the present application, a negative electrode composition is provided in which the negative electrode active material is at least about 40 parts by weight based on 100 parts by weight of the negative electrode composition.

[0101] In another embodiment, the negative electrode active material may be included in an amount of about 40 parts by weight or more, for example, about 60 parts by weight or more, about 65 parts by weight or more, or about 70 parts by weight or more, and may be included in an amount of about 95 parts by weight or less, about 90 parts by weight or less, or about 85 parts by weight or less, based on 100 parts by weight of the negative electrode composition.

[0102] The negative electrode composition according to the present application uses a negative electrode active material that satisfies a specific crystal grain size capable of controlling the volume expansion rate during the charge and discharge process even when a silicon-based active material with a significantly high capacity is used within the above range, so that the performance of the negative electrode is not deteriorated even within the above range, and the output characteristics during charge and discharge are excellent.

[0103] Previously, graphite compounds were typically used solely as negative electrode active materials. However, with the increasing demand for high-capacity batteries, attempts to mix silicon-based active materials to increase capacity have been increasing. However, even if the properties of silicon-based active materials themselves are adjusted as described above, the rapid expansion of volume during the charge / discharge process can cause some problems, damaging the conductive path formed within the negative electrode active material layer.

[0104] In one embodiment of the present application, the negative electrode conductive material may include at least one selected from a dot-shaped conductive material, a planar conductive material, and a linear conductive material.

[0105] In one embodiment of the present application, the dot-shaped conductive material can be used to improve conductivity of the negative electrode, and refers to a dot-shaped or spherical conductive material that has conductivity without causing chemical change. For example, the dot-shaped conductive material may be at least one selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and according to one embodiment, may include carbon black in that it implements relatively high conductivity and has excellent dispersibility.

[0106] In one embodiment of the present application, the dot-shaped conductive material has a BET specific surface area of ​​about 40 m 2 / g or more than 70m 2 / g or less, for example, about 45m 2 / g or more than 65m 2 / g or less, or about 50m 2 / g or more than 60m 2 / g can be less.

[0107] In one embodiment of the present application, the dot-shaped conductive material can satisfy a volatile matter content of about 0.01% or more and 1% or less, for example, 0.01% or more and 0.3% or less, or 0.01% or more and 0.1% or less.

[0108] When the functional group content of the dot-shaped conductive material satisfies the above range, the functional groups present on the surface of the dot-shaped conductive material allow the dot-shaped conductive material to be smoothly dispersed within the solvent when water is used as the solvent. In the present invention, the functional group content of the dot-shaped conductive material can be reduced by using a specific silicon-based active material, thereby achieving an excellent effect in improving dispersibility.

[0109] In one embodiment of the present application, a dot-shaped conductive material having a functional group content within the above range is included together with a silicon-based active material, and the functional group content can be controlled by adjusting the degree of heat treatment of the dot-shaped conductive material.

[0110] In one embodiment of the present application, the particle size of the dot-shaped conductive material may be about 10 nm to 100 nm, for example, about 20 nm to 90 nm, or about 20 nm to 60 nm.

[0111] In one embodiment of the present application, the conductive material may include a planar conductive material.

[0112] The above-mentioned planar conductive material can improve conductivity by increasing planar contact between silicon particles within the cathode, and at the same time, suppress the disconnection of conductive paths due to volume expansion. The above-mentioned planar conductive material can be expressed as a plate-shaped conductive material or a bulk conductive material.

[0113] In one embodiment of the present application, the planar conductive material may include at least one selected from plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and may be, for example, plate-shaped graphite.

[0114] In one embodiment of the present application, the average particle diameter (D50) of the surface-shaped conductive material may be about 2 μm to 7 μm, for example, about 3 μm to 6 μm, or about 3.5 μm to 5 μm. When the above range is satisfied, the sufficient particle size facilitates dispersion without causing excessive viscosity increase in the negative electrode slurry. Therefore, the dispersion effect is excellent when dispersion is performed using the same equipment and time.

[0115] In one embodiment of the present application, the surface-shaped conductive material provides a negative electrode composition having a D10 of about 0.5 μm or more and 2.0 μm or less, a D50 of about 2.5 μm or more and 3.5 μm or less, and a D90 of about 6.5 μm or more and 15.0 μm or less.

[0116] In one embodiment of the present application, the planar conductive material may be a high-specific surface area planar conductive material having a high BET surface area; or a low-specific surface area planar conductive material.

[0117] In one embodiment of the present application, a high surface area surface conductive material or a low surface area surface conductive material can be used without limitation as the surface conductive material; however, since the surface conductive material according to the present application may be affected to some extent by dispersion effects on electrode performance, a low surface area surface conductive material that does not cause dispersion problems can be used.

[0118] In one embodiment of the present application, the surface-shaped conductive material has a BET specific surface area of ​​about 1 m 2 / g can be more than that.

[0119] In another embodiment, the surface-shaped conductive material has a BET surface area of ​​about 1 m 2 / g or more than 500m 2 / g or less, for example, about 5m 2 / g or more than 300m 2 / g or less, or about 5m 2 / g or more than 250m 2 / g can be less.

[0120] The planar conductive material according to the present application may be a planar conductive material with a high specific surface area; or a planar conductive material with a low specific surface area.

[0121] In another embodiment, the surface-shaped conductive material is a high surface area surface-shaped conductive material, and has a BET surface area of ​​about 50 m 2 / g or more than 500m 2 / g or less, for example, about 80m 2 / g or more than 300m2 / g or less, or about 100m 2 / g or more than 300m 2 / g can satisfy the range below.

[0122] In another embodiment, the surface-shaped conductive material is a low surface area surface-shaped conductive material, and has a BET surface area of ​​about 1 m 2 / g or more than 40m 2 / g or less, for example, about 5m 2 / g or more than 30m 2 / g or less, or about 5m 2 / g or more than 25m 2 / g can satisfy the range below.

[0123] Other conductive materials may include linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundle-type carbon nanotubes. The bundle-type carbon nanotubes may include a plurality of carbon nanotube units. Here, the term "bundle type" refers to a secondary shape in the form of a bundle or rope, in which a plurality of carbon nanotube units are arranged in a substantially identical orientation with their longitudinal axes aligned parallel or entangled, unless otherwise specified. The carbon nanotube units have a cylindrical shape of a graphite sheet with a nano-sized diameter and an sp2 bonding structure. At this time, the graphite sheets may exhibit conductor or semiconductor properties depending on the curling angle and structure. The above bundled carbon nanotubes can be uniformly dispersed during the manufacture of a cathode compared to entangled type carbon nanotubes, and can smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0124] In one embodiment of the present application, a negative electrode composition is provided in which the negative electrode conductive material is present in an amount of about 10 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the negative electrode composition.

[0125] In another embodiment, the negative electrode conductive material may be included in an amount of about 0.1 parts by weight or more and 40 parts by weight or less, for example, about 0.2 parts by weight or more and 30 parts by weight or less, or about 0.4 parts by weight or more and 25 parts by weight or less, or about 0.4 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the negative electrode composition.

[0126] In one embodiment of the present application, a negative electrode composition is provided, wherein the negative electrode conductive material includes a planar conductive material and a linear conductive material.

[0127] In one embodiment of the present application, the negative electrode composition is provided, wherein the negative electrode conductive material comprises about 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material and about 0.1 parts by weight or more and 20 parts by weight or less of the linear conductive material, based on 100 parts by weight of the negative electrode conductive material.

[0128] In another embodiment, the negative electrode conductive material may include about 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material, for example, about 85 parts by weight or more to 99.9 parts by weight or less, or about 95 parts by weight or more to 98 parts by weight or less, based on 100 parts by weight of the negative electrode conductive material.

[0129] In another embodiment, the cathode conductive material may include about 0.1 to 20 parts by weight of the linear conductive material, for example, about 0.1 to 15 parts by weight, or about 0.2 to 5 parts by weight, based on 100 parts by weight of the cathode conductive material.

[0130] In one embodiment of the present application, since the negative electrode conductive material includes a planar conductive material and a linear conductive material and satisfies the above composition and ratio, respectively, it does not have a significant effect on the life characteristics of an existing lithium secondary battery, and in the case of including a planar conductive material and a linear conductive material, the number of points at which charging and discharging are possible increases, resulting in excellent output characteristics at a high C-rate and a reduced amount of high-temperature gas generation.

[0131] In one embodiment of the present application, the cathode conductive material may be formed of a linear conductive material.

[0132] According to one embodiment, when a linear conductive material is used alone, the electrode tortuosity, which is a problem of silicon-based negative electrodes, can be simplified, thereby improving the electrode structure and thus reducing the movement resistance of lithium ions within the electrode.

[0133] In one embodiment of the present application, when the negative electrode conductive material comprises a linear conductive material alone, the negative electrode conductive material may comprise about 0.1 parts by weight or more and 5 parts by weight or less, for example, about 0.2 parts by weight or more and 3 parts by weight or less, or about 0.4 parts by weight or more and 1 part by weight or less, based on 100 parts by weight of the negative electrode composition.

[0134] The negative electrode conductive material according to the present application has a completely separate composition from the positive electrode conductive material applied to the positive electrode. The negative electrode conductive material according to the present application serves to secure the contact between silicon-based active materials, which undergo a significant volume expansion of the electrode due to charging and discharging, and the positive electrode conductive material serves to provide some conductivity while acting as a buffer during rolling, and is completely different in composition and function from the negative electrode conductive material of the present invention.

[0135] In addition, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different composition from the conductive material applied to a graphite-based active material. That is, the conductive material used in an electrode having a graphite-based active material simply has smaller particles than the active material, and thus has the characteristics of improving output characteristics and imparting some conductivity, and is completely different in composition and role from the negative electrode conductive material applied together with a silicon-based active material as in the present invention.

[0136] In one embodiment of the present application, the planar conductive material used as the aforementioned negative electrode conductive material has a structure and function different from those of carbon-based active materials typically used as negative electrode active materials. For example, the carbon-based active material used as the negative electrode active material may be artificial graphite or natural graphite, and refers to a material processed into a spherical or dot-shaped form to facilitate the storage and release of lithium ions.

[0137] The planar conductive material used as the negative electrode conductive material is a material in the form of a planar or plate, and can be expressed as plate-shaped graphite. In other words, it refers to a material included to maintain a conductive path within the negative electrode active material layer, and is not a material that plays a role in storing and releasing lithium, but rather a material that secures a conductive path in the form of a plate within the negative electrode active material layer.

[0138] In this application, the use of plate-shaped graphite as a conductive material means that it is processed into a planar or plate-shaped form and used as a material to secure a conductive path rather than to store or release lithium. In this case, the included negative electrode active material has high capacity characteristics for lithium storage and release, and can store and release all lithium ions delivered from the positive electrode.

[0139] In the present application, the use of a carbon-based active material as an active material means that it is processed into a dot or spherical shape and used as a material that plays a role in storing or releasing lithium.

[0140] In one embodiment of the present application, the carbon-based active material, artificial graphite or natural graphite, is in a dot-like shape and has a BET specific surface area of ​​about 0.1 m 2 / g or more than 4.5 m 2 / g or less can be satisfied. In addition, the plate-shaped graphite, which is a planar conductive material, has a BET surface area of ​​about 5 m in the form of a planar surface. 2 / g can be more than that.

[0141] In one embodiment of the present application, the negative electrode binder may include at least one selected from polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and materials in which hydrogens thereof are substituted with Li, Na, Ca, etc., and may also include various copolymers thereof.

[0142] The negative electrode binder according to one embodiment of the present application serves to hold the active material and conductive material in order to prevent distortion and structural deformation of the negative electrode structure when the volume of the silicon-based active material expands and relaxes. If the above-mentioned role is satisfied, all general binders can be applied, and for example, an aqueous binder or a PAM-based binder can be used.

[0143] In one embodiment of the present application, the negative electrode binder may be about 30 parts by weight or less, for example, about 25 parts by weight or less, or about 20 parts by weight or less, based on 100 parts by weight of the negative electrode composition, and according to one embodiment, may be about 5 parts by weight or more, or 10 parts by weight or more.

[0144] FIG. 2 is a flowchart exemplarily showing a method for manufacturing a negative electrode active material according to an embodiment of the present application. Referring to FIG. 2, the method for manufacturing a negative electrode active material according to an embodiment of the present application includes a step of melting a silicon raw material (S100); a step of cooling the melted silicon raw material by spraying it onto an ultra-vibration low-temperature substrate (S200); and a step of measuring the crystal grain size and (D90 - D10) / D50 of the silicon-based active material (S300). Thereafter, the method for manufacturing a negative electrode active material according to an embodiment of the present application includes a step of determining whether the crystal grain size measured in the measuring step is 1 nm or more and 300 nm or less, and whether the measured (D90 - D10) / D50 value is 2 or less (S400).

[0145] In the manufacturing method according to the present application, unlike spherical silicon particles formed by melting existing Metallurgical Grade Silicon (MG-Si) and gas atomizing it, a silicon-based active material having small crystal grains and a uniform particle size distribution of Equation 1 can be manufactured through a low-temperature sonicated substrate to which ultrasonic waves are applied. With the above-mentioned characteristics, crack formation in the active material due to lithium insertion / de-insertion can be suppressed, and the problem of reduced life performance due to uneven charge / discharge within the electrode can be solved as lithium ions are uniformly introduced into the lithium electrode due to the improvement in uniform particle size.

[0146] In the present application, a method for manufacturing a negative electrode active material is provided, wherein the vibration frequency of the ultra-vibration low-temperature substrate is about 1 kHz or more and 1500 kHz or less.

[0147] In another embodiment, the vibration frequency of the ultra-vibration low-temperature substrate may be about 1 kHz or more and 1500 kHz or less, for example, 5 kHz or more and 1300 kHz or less, or 10 kHz or more and 1000 kHz or less.

[0148] In one embodiment of the present application, a method for producing a negative electrode active material is provided, wherein the cooling temperature in the step of cooling the molten silicon raw material to form a silicon-based active material is about 20°C or less.

[0149] In another embodiment, the cooling temperature in the step of cooling the molten silicon raw material to form a silicon-based active material may be about 20°C or less, -20°C or more, or -10°C or more.

[0150] In the present application, the cooling is controlled by controlling the cooling temperature of the solvent using a cooling solvent. The cooling solvent may be used without limitation as long as the cooling temperature is satisfied, but according to one embodiment, water or ethylene glycol may be used.

[0151] The method for manufacturing a negative active material according to the present application applies the manufacturing process described above, and a silicon-based active material satisfying the crystal grain size and particle size distribution (Formula 1) can be obtained by controlling the cooling rate.

[0152] In one embodiment of the present application, a negative electrode for a lithium secondary battery is provided, including: a negative electrode current collector layer; and a negative electrode active material layer including a negative electrode composition according to the present application or a cured product thereof formed on one or both sides of the negative electrode current collector layer.

[0153] FIG. 3 is a diagram showing a laminated structure of an anode for a lithium secondary battery according to one embodiment of the present application. Referring to FIG. 3, a lithium secondary battery anode (100) including an anode active material layer (20) on one surface of an anode current collector layer (10) can be confirmed, and FIG. 4 shows that an anode active material layer (20) is formed on one surface of an anode current collector layer (10), but is not limited thereto, and for example, an anode active material layer (20) may be formed on both surfaces of an anode current collector layer (10).

[0154] In one embodiment of the present application, the negative electrode (100) for the lithium secondary battery can be formed by applying and drying a negative electrode slurry containing the negative electrode composition to one or both sides of a negative electrode current collector layer (10).

[0155] At this time, the cathode slurry may include the cathode composition described above; and a slurry solvent.

[0156] In one embodiment of the present application, the solid content included in the cathode slurry can satisfy a range of about 5% to 40% based on 100 parts by weight of the cathode slurry.

[0157] In another embodiment, the solid content included in the cathode slurry may be in a range of about 5% to 40%, for example, about 7% to 35%, or about 10% to 30%, based on 100 parts by weight of the cathode slurry.

[0158] When the solid content of the above negative electrode slurry satisfies the above range, the viscosity is appropriate when forming the negative electrode active material layer, so that the particle agglomeration phenomenon of the negative electrode composition is minimized, thereby efficiently forming the negative electrode active material layer.

[0159] In one embodiment of the present application, the slurry solvent can be used without limitation as long as it can dissolve the negative electrode composition, and for example, water or NMP (N-Methyl-2-pyrrolidone) can be used.

[0160] In one embodiment of the present application, the negative electrode current collector layer generally has a thickness of about 1 μm to 100 μm. The negative electrode current collector layer is not particularly limited as long as it has relatively high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0161] In the negative electrode for a lithium secondary battery provided according to one embodiment of the present application, the thickness of the negative electrode current collector layer is about 1 μm or more and 100 μm or less, and the thickness of the negative electrode active material layer is about 5 μm or more and 500 μm or less.

[0162] However, the thickness can be varied depending on the type and purpose of the cathode used and is not limited thereto.

[0163] In one embodiment of the present application, the porosity of the negative electrode active material layer can satisfy a range of about 10% or more and 60% or less.

[0164] In another embodiment, the porosity of the negative electrode active material layer can satisfy a range of about 10% to 60%, for example, about 20% to 50%, or about 30% to 45%.

[0165] The above porosity varies depending on the composition and content of the silicon-based active material, conductive material, and binder included in the negative electrode active material layer. By including the silicon-based active material and conductive material according to the present application in a specific composition and content portion, the above range is satisfied, and accordingly, the electrode has an appropriate range of electrical conductivity and resistance.

[0166] A lithium secondary battery provided according to one embodiment of the present application includes: a positive electrode; an anode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0167] FIG. 4 is a diagram showing a laminated structure of a lithium secondary battery according to one embodiment of the present application. Referring to FIG. 4, a lithium secondary battery negative electrode (100) including a negative electrode active material layer (20) on one surface of a negative electrode current collector layer (10) can be confirmed, and a lithium secondary battery positive electrode (200) including a positive electrode active material layer (40) on one surface of a positive electrode current collector layer (50) can be confirmed, and it is shown that the lithium secondary battery negative electrode (100) and the lithium secondary battery positive electrode (200) are formed in a laminated structure with a separator (30) interposed therebetween.

[0168] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and including the positive electrode active material.

[0169] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of about 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0170] The above positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3Lithium manganese composite oxide represented by O2 (wherein M is at least one selected from Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from Fe, Co, Ni, Cu, and Zn); LiMn2O4, etc., in which a part of Li in the chemical formula is replaced with an alkaline earth metal ion; but the present invention is not limited thereto. For example, the positive electrode may be Li-metal.

[0171] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0172] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, it can be used without special restrictions as long as it does not cause a chemical change and has electronic conductivity. For example, graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, etc., and one of these may be used alone or a mixture of two or more may be used.

[0173] In addition, the positive electrode binder plays a role of improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof may be used.

[0174] The separator above separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and a material having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity can be used. For example, a porous polymer film, such as a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous non-woven fabric, such as a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc., can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0175] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0176] In one embodiment, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0177] As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used.

[0178] Among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants, which relatively easily dissociate lithium salts and can therefore be used as non-aqueous solvents. By mixing and using low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate in an appropriate ratio with these cyclic carbonates, an electrolyte with relatively high electrical conductivity can be produced and can thus be used as a non-aqueous solvent.

[0179] The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte, for example, the anion of the lithium salt is F - , Cl - , I - , NO3- , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more types selected from may be used.

[0180] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, a cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery.

[0181] One embodiment of the present invention provides a battery module including the secondary battery as a unit cell and a battery pack including the same. The battery module and battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, and thus can be used as a power source for medium- to large-sized devices selected from electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0182] Hereinafter, examples are presented to help understand the present invention, but the examples presented below are only illustrative of the present disclosure, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended patent claims.

[0183] <Manufacturing Example>

[0184] <Preparation of negative active material of Example 1>

[0185] According to the manufacturing method according to Fig. 5, unlike the existing gas atomizing method, the substrate is sonicated and cooled at the same time to perform gas atomizing at a relatively lower temperature, thereby producing a silicon-based active material having a more uniform particle size distribution and relatively small-sized crystal grains.

[0186] Silicon raw materials were pulverized and heated to liquefy them, and then gas atomized. At this time, the substrate was sonicated to form a surface-phase wave in a liquid state so that particles could be formed with a more uniform size. In addition, during silicon particle crystallization, rapid cooling was used to suppress grain growth, and silicon-based active materials satisfying the properties shown in Table 1 were manufactured. Table 1 shows the properties of Examples 1-8 manufactured by varying the frequency applied to the sonication of the substrate, the solvent cooling temperature, and the type of cooling solvent.

[0187] <Manufacturing of negative active material of comparative example 1>

[0188] The manufacturing method according to Fig. 6 involves melting an existing silicon raw material and then gas atomizing it. For example, a silicon lump, MG-Si, is crushed using physical force, melted, and then gas atomized.

[0189] At this time, due to the influence of the liquid-gas surface tension during the gas atomizing process, a silicon-based active material with a smooth surface was formed, but the overall particle size distribution was wide and it had a relatively large crystal grain size. The physical properties can be confirmed in Table 1 below. Table 1 shows the physical properties of Comparative Examples 1-7 manufactured by varying the frequency applied to the sonication of the substrate, the solvent cooling temperature, and the type of cooling solvent.

[0190] Grain size (nm) Span (Equation 1 value) Cooling solvent Solvent Cooling temperature (℃) Vibration frequency (kHz) Example 1 25 11.96 Water 20 10 Example 22 43 1.83 Water 20 1000 Example 32 30 1.90 Water 10 10 Example 42 19 1.73 Water 10 1000 Example 52 211.89 Ethylene glycol 0 10 Example 62 07 1.64 Ethylene glycol 0 1000 Example 7 18 31.86 Ethylene glycol-10 10 Example 8 17 6 ​​1.61 Ethylene glycol-10 1000 Comparative example 12 80 2.53 --- Comparative example 23 10 2.07 --- 10 Comparative example 33 34 2.04 --- 1000 Comparative example 42702.51 Water 20-Comparative Example 52562.44 Water 10-Comparative Example 62412.37 Ethylene Glycol 0-Comparative Example 72252.33 Ethylene Glycol-10-

[0191] <Manufacturing of the cathode>

[0192] A negative electrode slurry was prepared by adding a negative electrode active material including the above silicon-based active material, a first conductive material, a second conductive material, and polyacrylamide as a binder in a weight ratio of 80:9.6:0.4:10 to distilled water as a solvent for forming a negative electrode slurry (solid content concentration 25 wt%).

[0193] For example, the first challenge material is a plate-shaped graphite (specific surface area: 17 m 2 / g, average particle diameter (D50): 3.5 μm), and the second conductive material was SWCNT.

[0194] As a mixing method, the first and second conductive materials, binder and water were dispersed using a homogenous mixer at 2500 rpm for 30 minutes, and then the silicon-based active material was added and dispersed at 2500 rpm for 30 minutes to produce a negative electrode slurry.

[0195] The negative electrode slurry is applied at 85 mg / 25 cm on both sides of a copper current collector (thickness: 8 μm) as a negative electrode current collector layer. 2 The coating was carried out with a loading amount of , rolled (roll pressed), and dried in a vacuum oven at 130°C for 10 hours to form a negative electrode active material layer (thickness: 33 μm), which was used as a negative electrode (thickness of negative electrode: 41 μm, porosity of negative electrode: 40.0%).

[0196] <Manufacturing of secondary batteries>

[0197] LiNi as a cathode active material 0.6 Co 0.2 Mn 0.2 O2 (average particle size (D50): 15㎛), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent for forming a cathode slurry at a weight ratio of 97:1.5:1.5 to prepare a cathode slurry (solid content concentration: 78 wt%).

[0198] The positive electrode slurry was applied to both sides of an aluminum current collector (thickness: 12㎛) as a positive electrode collector at a density of 537mg / 25cm.2 A positive electrode was manufactured by coating with a loading amount, rolling, and drying in a vacuum oven at 130°C for 10 hours to form a positive electrode active material layer (thickness: 65 μm) (positive electrode thickness: 77 μm, porosity 26%).

[0199] A lithium secondary battery was manufactured by interposing a polyethylene separator between the positive electrode and the negative electrode of the above examples and comparative examples and injecting an electrolyte.

[0200] The above electrolyte was an organic solvent containing fluoroethylene carbonate (FEC) and diethyl carbonate (DMC) mixed in a volume ratio of 10:90, vinylene carbonate added at 3 wt% based on the total weight of the electrolyte, and LiPF6 added as a lithium salt at a concentration of 1 M.

[0201] <Experimental Example>

[0202] Experimental Example 1: Cycle Life Data

[0203] The secondary batteries containing the negative electrodes manufactured in the above examples and comparative examples were subjected to a life evaluation using an electrochemical charger / discharger, and the capacity retention rate was evaluated. The secondary batteries were subjected to an in-situ cycle test at 4.2-3.0 V 1C / 0.5C, and the capacity retention rate was measured by charging / discharging at 0.33C / 0.33C (4.2-3.0 V) every 50 cycles during the test.

[0204] Life retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at 1st cycle)} Х 100

[0205] Experimental Example 2: Cycle Resistance Increase Rate

[0206] In the above experimental example 1, the capacity retention rate was measured by performing 0.33C / 0.33C charge / discharge (4.2-3.0V) every 50 cycles during the test, and then the resistance increase rate was compared and analyzed by measuring the total resistance by discharging at 2.5C pulse at SOC50.

[0207] For the above resistance increase rate measurement evaluation, data at 200 cycles were calculated, and the results were as shown in Table 2 below.

[0208] Life maintenance rate (%) Resistance increase rate (%) Example 174.829 Example 275.325 Example 376.223 Example 478.321 Example 580.920 Example 682.718 Example 783.117 Example 885.413 Comparative example 16149 Comparative example 261.547 Comparative example 361.346 Comparative example 463.440 Comparative example 563.738 Comparative example 664.235 Comparative example 767.332

[0209] In the case of the negative active material according to one embodiment of the present invention, it is possible to form droplets with a particle size in the range of Equation 1 by forming a standing wave on the surface that is atomized through the power of ultrasonication, and the main feature is that it has a specific range of particle sizes due to a decrease in crystal grain growth as a result of an increase in the cooling rate by using a low-temperature substrate instead of the existing air. Accordingly, it was confirmed that the formation of cracks in the active material due to lithium insertion / de-insertion can be suppressed by reducing the crystal grain size, and also, by improving the particle size to the range of Equation 1, it has the feature of solving the problem of reduced life performance due to uneven charge / discharge within the electrode as lithium ions are uniformly introduced into the lithium electrode.

[0210] Referring to Table 2, in terms of adjusting the range of Equation 1, it was confirmed that the cell had better performance in life evaluation and resistance evaluation when the frequency was formed high within a specific range and the temperature was manufactured low within a specific range.

[0211] In the case of Comparative Example 1, cooling and sonication vibration were not applied, in the case of Comparative Examples 2 and 3, cooling was not applied, and in the case of Comparative Examples 4 to 7, the cooling process was applied but sonication vibration was not applied.

[0212] In cases where both sonication vibration and cooling were performed, the grain size according to the present application and the range of Equation 1 were satisfied. In the case of Comparative Examples 1 to 3, the size of the grains was formed larger than that of the examples because the cooling process was not performed, and the range of Equation 1 was also confirmed to be formed larger. In the case of Comparative Examples 4 to 7, the grain size was included in the range of the present application because the cooling process was performed, but it was confirmed that the grain size relationship (Equation 1) was not satisfied because the sonication vibration was not performed.

[0213] In the case of Comparative Examples 1 to 7, it was confirmed that lithium ions did not enter the lithium electrode evenly because the crystal grain size and / or the range of Equation 1 were not satisfied, and thus, a problem of reduced life performance occurred due to uneven charging and discharging within the electrode.

[0214] Although the present disclosure has been described above with reference to embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the various embodiments of the present disclosure may be made without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims

1. Contains a silicon-based active material having a crystal grain size of 300 nm or less, The above silicon-based active material has a value defined by the following formula 1 of 2.00 or less, The above silicon-based active material is SiOx (x=0) and SiOx (0 <x<2)로 부터 선택되는 1 이상을 포함하며, 상기 실리콘계 활물질 100 중량부 기준 상기 SiOx (x=0)를 약 70 중량부 이상 포함하는 것인 음극 활물질: [Formula 1] (D90 - D10) / D50 In the above equation 1, D90, D10 and D50 represent the diameters of particles corresponding to 90%, 10% and 50% by volume in the size distribution, respectively.

2. In claim 1, a negative electrode active material having a crystal grain size of SiOx (x=0) of 300 nm or less.

3. In claim 1, The above silicon-based active material is a negative electrode active material including a crystal structure having a crystal grain distribution of 1 nm or more and 300 nm or less.

4. In claim 1, A negative electrode active material having an average particle diameter (D50) of 1 μm or more and 9 μm or less of the above silicon-based active material.

5. In claim 1, The crystal grain size of the above silicon-based active material is 1 nm or more and 300 nm or less, A negative electrode active material having an average particle diameter (D50) of 3 μm or more and 8 μm or less of the above silicon-based active material.

6. Step of melting silicon raw material; and A method for manufacturing a negative electrode active material, comprising: a step of cooling the molten silicon raw material to form a silicon-based active material; The step of cooling the molten silicon raw material to form a silicon-based active material includes the step of cooling the molten silicon raw material by spraying it onto an ultra-vibration low-temperature substrate. The above silicon-based active material has a crystal grain size of 300 nm or less, The above silicon-based active material is a method for manufacturing a negative electrode active material having a value of 2.00 or less as defined by the following formula 1: [Formula 1] (D90 - D10) / D50 In the above equation 1, D90, D10 and D50 represent the diameters of particles corresponding to 90%, 10% and 50% by volume in the size distribution, respectively.

7. In claim 6, A method for manufacturing a negative electrode active material, wherein the vibration frequency of the above ultra-vibration low-temperature substrate is 1 kHz or more and 1500 kHz or less.

8. In claim 6, A method for manufacturing a negative electrode active material, wherein the cooling temperature in the step of cooling the above-mentioned molten silicon raw material to form a silicon-based active material is 20°C or less.

9. A negative electrode composition comprising a negative electrode active material according to any one of claims 1 to 5; a negative electrode conductive material; and a negative electrode binder.

10. In claim 9, A negative electrode composition in which the negative electrode active material is at least 40 parts by weight based on 100 parts by weight of the negative electrode composition.

11. In claim 9, The above negative electrode conductive material is a planar conductive material; and a negative electrode composition including a linear conductive material.

12. In claim 11, The negative electrode composition comprises the above-mentioned negative electrode conductive material in an amount of 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material based on 100 parts by weight of the above-mentioned negative electrode conductive material; and the above-mentioned linear conductive material in an amount of 0.1 parts by weight or more and 20 parts by weight or less.

13. In claim 9, A cathode composition wherein the cathode conductive material is present in an amount of 20 parts by weight or less based on 100 parts by weight of the cathode composition.

14. A negative electrode current collector layer; and a negative electrode active material layer provided on one or both sides of the negative electrode current collector layer, A negative electrode for a lithium secondary battery, wherein the negative electrode active material layer comprises the negative electrode composition according to claim 9 or a cured product thereof.

15. In claim 14, The thickness of the above negative electrode current collector layer is 1 μm or more and 100 μm or less, A negative electrode for a lithium secondary battery, wherein the thickness of the negative electrode active material layer is 5 μm or more and 500 μm or less.

16. Bipolar; A negative electrode for a lithium secondary battery according to claim 14; A separator provided between the anode and the cathode; and A lithium secondary battery comprising an electrolyte.

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